全文获取类型
收费全文 | 14579篇 |
免费 | 301篇 |
国内免费 | 1篇 |
专业分类
财政金融 | 2637篇 |
工业经济 | 1123篇 |
计划管理 | 2397篇 |
经济学 | 3093篇 |
综合类 | 116篇 |
运输经济 | 94篇 |
旅游经济 | 215篇 |
贸易经济 | 2311篇 |
农业经济 | 829篇 |
经济概况 | 2020篇 |
信息产业经济 | 1篇 |
邮电经济 | 45篇 |
出版年
2021年 | 94篇 |
2020年 | 137篇 |
2019年 | 228篇 |
2018年 | 325篇 |
2017年 | 308篇 |
2016年 | 307篇 |
2015年 | 198篇 |
2014年 | 322篇 |
2013年 | 1274篇 |
2012年 | 432篇 |
2011年 | 431篇 |
2010年 | 354篇 |
2009年 | 436篇 |
2008年 | 426篇 |
2007年 | 373篇 |
2006年 | 357篇 |
2005年 | 308篇 |
2004年 | 313篇 |
2003年 | 323篇 |
2002年 | 315篇 |
2001年 | 267篇 |
2000年 | 301篇 |
1999年 | 254篇 |
1998年 | 251篇 |
1997年 | 230篇 |
1996年 | 244篇 |
1995年 | 208篇 |
1994年 | 223篇 |
1993年 | 225篇 |
1992年 | 238篇 |
1991年 | 239篇 |
1990年 | 228篇 |
1989年 | 199篇 |
1988年 | 173篇 |
1987年 | 164篇 |
1986年 | 189篇 |
1985年 | 278篇 |
1984年 | 252篇 |
1983年 | 225篇 |
1982年 | 222篇 |
1981年 | 219篇 |
1980年 | 215篇 |
1979年 | 202篇 |
1978年 | 180篇 |
1977年 | 173篇 |
1976年 | 171篇 |
1975年 | 156篇 |
1974年 | 122篇 |
1973年 | 120篇 |
1972年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
This paper examines the longevity of foreign entries. Hypotheses are developed on the mode (start-ups vs. acquisitions) and ownership structure (wholly owned vs. joint ventures) in relation to cultural distance. The hypotheses are tested within a framework of organizational learning, using data on 225 entries that 13 Dutch firms carried out from 1966 onwards. Results show that the presence of cultural barriers punctuates an organization's learning. Cultural distance is a prominent factor in foreign entry whenever this involves another firm, requiring the firm to engage in ‘double layered acculturation.’ We also identify locational ‘paths of learning.’ The longevity of acquisitions is positively influenced by prior entries of the firm in the same country. Similarly, the longevity of foreign entries, in which the firm has a majority stake, improves whenever the expanding firm engaged in prior entries in the same country and in other countries in the same cultural block. 相似文献
152.
153.
154.
155.
Hans G. Ehrbar 《Metroeconomica》1993,44(3):215-238
A revised definition of efficiency compares portfolios with different net worths. One axiom rules out instantaneous riskless gains, the other asserts that it costs money to buy good portfolios. Unlimited short sales are allowed. Portfolios which cannot be improved at any price are called absolutely efficient. The geometry of the mean-standard deviation frontiers is governed by three “efficient set constants”. A few results regarding efficient portfolios must be modified, and a new version of the security line equation is proposed. Explicit formulas are given: no need to use different formulas for singular or non-singular covariance matrix. 相似文献
156.
157.
Metallic structured packings have found increasing use in the cryogenic distillation of air. An experimental program was performed to test the flammability of selected metal packings under simulated high oxygen concentration operating conditions. Aluminum flammability in gaseous oxygen has been shown to be very dependent upon argon dilution, and in the presence of liquid oxygen, strong energy releases have been observed. Brass packing exhibited an unexpectedly high relative flammability whereas copper has been found to be non-flammable in all tested oxygen purities. These findings suggest the use of copper structured packing in higher purity GOX/LOX regions of an air separation distillation column and aluminum structured packing in the remainder of the column. 相似文献
158.
Laurence G. Britton 《Process Safety Progress》1991,10(1):27-44
Combustible liquids may self-heat in porous insulation yielding smoldering or flaming combustion. In Part I the problem is reviewed and practical measures discussed. Using two-inch cubes of insulation and a standardized procedure, Spontaneous Ignition Temperatures (SITs) ranging from 55-184 C are reported for a series of combustible liquids. The application of a self-heating parameter Z = (AIT)/(AIT-FP), where AIT is autoignition temperature and FP is closed cup flash-point (both in Celsius), is examined. The “Z” parameter gives some indication of materials that will self-heat and those that will evaporate. For Z > 1.61 ignition occurred for all the liquids tested. Evaporation usually occurred for materials with Z < 1.35. It was found that some water-reactive or peroxide-forming materials can ignite where only evaporation would be predicted from Z value considerations. An important example of a water-reactive material is ethylene oxide (EO); the importance of EO insulation fires is that under certain conditions explosive decomposition of EO contained in the equipment can be initiated. It was previously determined that ethylene oxide reacts in porous, refractory insulations forming low molecular weight polyethylene glycols. The formation rate depends on temperature and the type and condition (particularly water content) of the insulation. Unlike EO the glycols have low volatility and may accumulate over time to several times the mass of some insulations. Under certain conditions the glycols can ignite spontaneously. In Part II experiments carried out to examine this phenomenon are discussed. Where process temperatures are above the SIT (but below the AIT), cellular glass insulation will minimize the risk of insulation fires. One disadvantage, especially for thermally unstable materials such as EO, is that cellular glass has poor fire endurance properties. The use of a realistic fire endurance test to specify insulation thickness and additional measures such as stainless steel jackets are described. Alternatives to the use of cellular glass are discussed. When selecting an insulation system, it should be determined whether an insulation fire might occur and the loss potential from such an event should be evaluated. 相似文献
159.
A. G. Barve 《The World Economy》1991,14(2):239-242
Dynamics and Conflict in Regional Structura1 Change—Essay in Honor of Walter Isard Volume 2 Practical Methods of Regional Science and Empirical Applications—Selected Papers of Walter Isard, Volume 2 Department of Economics Loughborough University Export Promotion Strategies—Theory and Evidence from Developing Countries Commonwealth Secretariat Export Market Development Division Human Development Report 1990 for the United Nations Development Programme (UNDP) (New York and Oxford: University of Nottingham The World Bank and the Environment—First Annual Report Fiscal 1990, The World Bank (New York: The World Bank, 1990 London Environmental Economics Centre University College London The European Communities' Single Market: The Challenge of 1992 for Sub-Saharan Africa Loughborough University 相似文献
160.
Thomas G. Grumbles 《Process Safety Progress》1990,9(2):87-90
This paper presents the results of an industry survey that was sponsored by the Ethylene Oxide Industry Council (EOIC). The EOIC operates as a special program of the Chemical Manufacturers Association. The members of EOIC account for over 85 percent of domestic production of EtO and cover a broad range of EtO users, including ethoxylators and sterilizers. The survey was done to collect current information in anticipation of responding to a proposed OSHA rulemaking for a short-term exposure limit for EtO. Specifically, the study was designed to collect information on the following:
- 1. History of the establishment of company EtO exposure guidelines.
- 2. Current EtO workplace exposure monitoring practices, capabilities and methods.
- 3. Current workplace exposure levels: Eight hour and short-term.
- 4. Engineering control, respirator, and ancillary costs for compliance with the 1.0 Permissible Exposure Limit (PEL) and projected costs for compliance with a 5.0 ppm or 10.0 ppm Short–term Exposure Limit (STEL).